Controlling transitions in optically switchable devices

ABSTRACT

This disclosure provides systems, methods, and apparatus for controlling transitions in an optically switchable device. In one aspect, a controller for a tintable window may include a processor, an input for receiving output signals from sensors, and instructions for causing the processor to determine a level of tint of the tintable window, and an output for controlling the level of tint in the tintable window. The instructions may include a relationship between the received output signals and the level of tint, with the relationship employing output signals from an exterior photosensor, an interior photosensor, an occupancy sensor, an exterior temperature sensor, and a transmissivity sensor. In some instances, the controller may receive output signals over a network and/or be interfaced with a network, and in some instances, the controller may be a standalone controller that is not interfaced with a network.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/449,235, by Brown et al., filed on Apr. 17, 2012 and entitledCONTROLLING TRANSITIONS IN OPTICALLY SWITCHABLE DEVICES, which isincorporated herein by reference in its entirety and for all purposes.Also, this application is related to U.S. patent application Ser. No.13/049,756, naming Brown et al. as inventors, filed on Mar. 16, 2011 andentitled MULTIPURPOSE CONTROLLER FOR MULTISTATE WINDOWS, to U.S. patentapplication Ser. No. 13/449,248, naming Brown as inventor, filed on Apr.17, 2012 and entitled CONTROLLER FOR OPTICALLY SWITCHABLE WINDOWS, andto U.S. patent application Ser. No. 13/449,251, naming Brown asinventor, filed on Apr. 17, 2012 and entitled CONTROLLER FOROPTICALLY-SWITCHABLE WINDOWS, all of which applications are incorporatedherein by reference in their entireties and for all purposes.

FIELD The embodiments disclosed herein relate generally toelectrochromic devices, more particularly to controllers and relatedalgorithms for electrochromic windows. BACKGROUND

Electrochromism is a phenomenon in which a material exhibits areversible electrochemically-mediated change in an optical property whenplaced in a different electronic state, typically by being subjected toa voltage change. The optical property is typically one or more ofcolor, transmittance, absorbance, and reflectance. One well knownelectrochromic material is tungsten oxide (WO₃). Tungsten oxide is acathodic electrochromic material in which a coloration transition,transparent to blue, occurs by electrochemical reduction.

Electrochromic materials may be incorporated into, for example, windowsfor home, commercial and other uses. The color, transmittance,absorbance, and/or reflectance of such windows may be changed byinducing a change in the electrochromic material, that is,electrochromic windows are windows that can be darkened or lightenedelectronically. A small voltage applied to an electrochromic device (EC)of the window will cause them to darken; reversing the voltage causesthem to lighten. This capability allows control of the amount of lightthat passes through the windows, and presents an opportunity forelectrochromic windows to be used as energy-saving devices.

While electrochromism was discovered in the 1960's, EC devices, andparticularly EC windows, still unfortunately suffer various problems andhave not begun to realize their full commercial potential despite manyrecent advancements in EC technology, apparatus and related methods ofmaking and/or using EC devices.

SUMMARY

Systems, methods, and apparatus for controlling transitions in anoptically switchable device are disclosed herein.

In one aspect, a method of limiting energy consumption in a facilityhaving at least one tintable window between an interior and exterior ofthe facility is provided. The level of tinting in the tintable windowcan be controlled automatically. The method includes receiving outputsignals from any two or more sensors selected from the group consistingof an exterior photosensor, an interior photosensor, an occupancysensor, an exterior temperature sensor, and a transmissivity sensorwhich detects light passing through the tintable window from theexterior. A level of tint for the tintable window is determined using arelationship between the received output signals and the level of tint.Instructions to change the tint of the tintable window to the level oftint determined are provided.

In another aspect, a controller for a tintable window for a facilityhaving at least one tintable window between an interior and exterior ofthe facility is provided. The controller includes a processor or controlcircuit, at least one input for receiving output signals from one ormore sensors, and instructions for causing the processor or controlcircuit to determine a level of tint in the tintable window by using arelationship between the received output signals and the level of tint.The relationship employs output signals from any two or more sensorsselected from the group consisting of an exterior photosensor, aninterior photosensor, an occupancy sensor, an exterior temperaturesensor, and a transmissivity sensor which detects light passing throughthe tintable window from the exterior. The controller further includesat least one output for controlling, directly or indirectly, the levelof tint in the tintable window.

In another aspect, a system for controlling energy consumption in afacility that contains a tintable window between an interior andexterior of the facility is provided. The system includes a buildingmanagement system, a lighting control panel, a network over which thebuilding management system and the lighting control panel communicate,and a controller for the tintable window. The controller includesinstructions for determining a level of tint in the tintable window byusing a relationship between received output signals and the level oftint. The relationship employs output signals from any two or moresensors selected from the group consisting of an exterior photosensor,an interior photosensor, an occupancy sensor, an exterior temperaturesensor, and a transmissivity sensor which detects light passing throughthe tintable window from the exterior. The controller further includesat least one output for controlling, directly or indirectly, the levelof tint in the tintable window.

In another aspect, a method of minimizing energy consumption in afacility having a tintable window between an exterior and an interior ofthe facility is provided. The tintable window has an adjustable level oftint controllable from a controller. The method includes receiving asignal indicating energy or power consumption by a heating system, acooling system, and/or lighting within the facility, determining a levelof tint for the tintable window using the signal indicating energy orpower consumption of a device or system within the facility, andproviding instructions to set the level of tint in the tintable windowto the determined level of tint.

In another aspect, a controller for a tintable window for a facilityhaving at least one tintable window between an interior and exterior ofthe facility is provided. The controller includes a processor or controlcircuit, at least one input for receiving output signals from one ormore sensors, and instructions for causing the processor or controlcircuit to determine a level of tint in the tintable window by using arelationship between the received output signals and the level of tint.The relationship employs output signals from an exterior photosensor, aninterior photosensor, an outside temperature sensor, and a tint command.The controller further includes at least one output for controlling,directly or indirectly, the level of tint in the tintable window.

In another aspect, a method of limiting energy consumption in a facilityhaving at least one tintable window between an interior and exterior ofthe facility is provided. The level of tinting in the tintable windowcan be controlled automatically. The method includes receiving signalsindicating a level of exterior irradiance received at or proximate thetintable window and determining a level of tint for the tintable windowusing a relationship between the received output signals and the levelof tint. The relationship requires (i) transitioning from a first darkertint level to a second lighter tint level when the received level ofirradiance passes a first threshold and (ii) transitioning from thesecond lighter tint level to the first darker tint level when thereceived level of irradiance passes a second threshold. The first andsecond thresholds are different. The method further includes providinginstructions to change the tint of the tintable window to the determinedlevel of tint.

These and other features and advantages will be described in furtherdetail below, with reference to the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description can be more fully understood whenconsidered in conjunction with the drawings in which:

FIGS. 1A-1C show schematic diagrams of electrochromic devices formed onglass substrates, i.e., electrochromic lites.

FIGS. 2A and 2B show cross-sectional schematic diagrams of theelectrochromic lites as described in relation to FIGS. 1A-C integratedinto an IGU.

FIG. 3A depicts a schematic cross-section of an electrochromic device.

FIG. 3B depicts a schematic cross-section of an electrochromic device ina bleached state (or transitioning to a bleached state).

FIG. 3C depicts a schematic cross-section of the electrochromic deviceshown in FIG. 3B, but in a colored state (or transitioning to a coloredstate).

FIG. 4 depicts a block diagram of a window controller.

FIG. 5 depicts a schematic diagram of a room including an electrochromicwindow and a plurality of sensors.

FIG. 6 shows a function that may be used to determine the level of tintof an electrochromic window.

FIG. 7 shows a schedule of weighting constants that may be used with thefunction shown in FIG. 6.

FIG. 8 shows a flow chart of a method for limiting the energyconsumption in a room having at least one tintable window between aninterior and exterior of the room.

FIG. 9 shows a flow chart of a method of operating a tintable windowinstalled between an interior and exterior of a room.

FIG. 10 shows a plot of illuminance versus time for an exteriorphotosensor over a 24-hour period.

FIG. 11 depicts a schematic diagram of an embodiment of a buildingmanagement system.

FIG. 12 depicts a block diagram of an embodiment of a building network.

DETAILED DESCRIPTION

Window controllers described herein are used to control tintablewindows, including electrochromic windows. Virtually any tintable and/orreflective window or mirror will work with the window controllersdescribed herein. For example, non-electrochromic optically switchabledevices such liquid crystal devices and suspended particle devices maybe used with the described window controllers.

The window controllers described herein significantly augmentenvironmental control in a building, for example, when the windowcontrollers are integrated with a building management system (BMS).Interrelationships between window performance, microclimate sensing, andenvironmental control are described in more detail below.

For example, as shown in FIGS. 5, 6, and 7, a standalone windowcontroller may receive input from various sensors, including an exteriorphotosensor, an interior photosensor, a temperature sensor, an interiortransmissivity sensor, an occupancy sensor, and a power meter. Theseinputs may be processed by the window controller to determine a desiredtint for a tintable window using, for example, a function (e.g., seeFIG. 6) or a lookup table. The function or lookup table may change withthe time of day or the day of the year to account for the changes insunlight incident upon the tintable window (e.g., see FIG. 7). Further,tintable windows and a window controller may be integrated into abuilding including a building network or a BMS (e.g., see FIGS. 11 and12). The window controller may interface with the different systems ofthe building to aid in the control of the environment in the building.

OVERVIEW OF ELECTROCHROMIC DEVICES

It should be understood that while the disclosed embodiments focus onelectrochromic (EC) windows (also referred to as smart windows), theconcepts disclosed herein may apply to other types of tintable windows.For example, a window incorporating a liquid crystal device or asuspended particle device, instead of an electrochromic device, could beincorporated in any of the disclosed embodiments.

In order to orient the reader to the embodiments of systems, windowcontrollers, and methods disclosed herein, a brief discussion ofelectrochromic devices is provided.

This initial discussion of electrochromic devices is provided forcontext only, and the subsequently described embodiments of systems,window controllers, and methods are not limited to the specific featuresand fabrication processes of this initial discussion.

A particular example of an electrochromic lite is described withreference to FIGS. 1A-1C, in order to illustrate embodiments describedherein. FIG. 1A is a cross-sectional representation (see cut X-X′ ofFIG. 1C) of an electrochromic lite, 100, which is fabricated startingwith a glass sheet, 105. FIG. 1B shows an end view (see perspective Y-Y′of FIG. 1C) of EC lite 100, and FIG. 1C shows a top-down view of EC lite100. FIG. 1A shows the electrochromic lite after fabrication on glasssheet 105, edge deleted to produce area, 140, around the perimeter ofthe lite. The electrochromic lite has also been laser scribed and busbars have been attached. The glass lite 105 has a diffusion barrier,110, and a first transparent conducting oxide (TCO), 115, on thediffusion barrier. In this example, the edge deletion process removesboth TCO 115 and diffusion barrier 110, but in other embodiments onlythe TCO is removed, leaving the diffusion barrier intact. The TCO 115 isthe first of two conductive layers used to form the electrodes of theelectrochromic device fabricated on the glass sheet. In this example,the glass sheet includes underlying glass and the diffusion barrierlayer. Thus, in this example, the diffusion barrier is formed, and thenthe first TCO, an EC stack, 125, (e.g., having electrochromic, ionconductor, and counter electrode layers), and a second TCO, 130, areformed. In one embodiment, the electrochromic device (EC stack andsecond TCO) is fabricated in an integrated deposition system where theglass sheet does not leave the integrated deposition system at any timeduring fabrication of the stack. In one embodiment, the first TCO layeris also formed using the integrated deposition system where the glasssheet does not leave the integrated deposition system during depositionof the EC stack and the (second) TCO layer. In one embodiment, all ofthe layers (diffusion barrier, first TCO, EC stack, and second TCO) aredeposited in the integrated deposition system where the glass sheet doesnot leave the integrated deposition system during deposition. In thisexample, prior to deposition of EC stack 125, an isolation trench, 120,is cut through TCO 115 and diffusion barrier 110. Trench 120 is made incontemplation of electrically isolating an area of TCO 115 that willreside under bus bar 1 after fabrication is complete (see FIG. 1A). Thisis done to avoid charge buildup and coloration of the EC device underthe bus bar, which can be undesirable.

After formation of the EC device, edge deletion processes and additionallaser scribing are performed. FIG. 1A depicts areas 140 where the devicehas been removed, in this example, from a perimeter region surroundinglaser scribe trenches, 150, 155, 160, and 165. Trenches 150, 160 and 165pass through the EC stack and also through the first

TCO and diffusion barrier. Trench 155 passes through second TCO 130 andthe EC stack, but not the first TCO 115. Laser scribe trenches 150, 155,160, and 165 are made to isolate portions of the EC device, 135, 145,170, and 175, which were potentially damaged during edge deletionprocesses from the operable EC device. In this example, laser scribetrenches 150, 160, and 165 pass through the first TCO to aid inisolation of the device (laser scribe trench 155 does not pass throughthe first TCO, otherwise it would cut off bus bar 2's electricalcommunication with the first TCO and thus the EC stack). The laser orlasers used for the laser scribe processes are typically, but notnecessarily, pulse-type lasers, for example, diode-pumped solid statelasers. For example, the laser scribe processes can be performed using asuitable laser from IPG Photonics (of Oxford, Mass.), or from Ekspla (ofVilnius, Lithuania). Scribing can also be performed mechanically, forexample, by a diamond tipped scribe. One of ordinary skill in the artwould appreciate that the laser scribing processes can be performed atdifferent depths and/or performed in a single process whereby the lasercutting depth is varied, or not, during a continuous path around theperimeter of the EC device. In one embodiment, the edge deletion isperformed to the depth of the first TCO.

After laser scribing is complete, bus bars are attached. Non-penetratingbus bar (1) is applied to the second TCO. Non-penetrating bus bar (2) isapplied to an area where the device was not deposited (e.g., from a maskprotecting the first TCO from device deposition), in contact with thefirst TCO or, in this example, where an edge deletion process (e.g.,laser ablation using an apparatus having a XY or XYZ galvanometer) wasused to remove material down to the first TCO. In this example, both busbar 1 and bus bar 2 are non-penetrating bus bars. A penetrating bus baris one that is typically pressed into and through the EC stack to makecontact with the TCO at the bottom of the stack. A non-penetrating busbar is one that does not penetrate into the EC stack layers, but rathermakes electrical and physical contact on the surface of a conductivelayer, for example, a TCO.

The TCO layers can be electrically connected using a non-traditional busbar, for example, a bus bar fabricated with screen and lithographypatterning methods. In one embodiment, electrical communication isestablished with the device's transparent conducting layers via silkscreening (or using another patterning method) a conductive ink followedby heat curing or sintering the ink. Advantages to using the abovedescribed device configuration include simpler manufacturing, forexample, and less laser scribing than conventional techniques which usepenetrating bus bars.

After the bus bars are connected, the device is integrated into aninsulated glass unit (IGU), which includes, for example, wiring the busbars and the like. In some embodiments, one or both of the bus bars areinside the finished IGU, however in one embodiment one bus bar isoutside the seal of the IGU and one bus bar is inside the IGU. In theformer embodiment, area 140 is used to make the seal with one face ofthe spacer used to form the IGU. Thus, the wires or other connection tothe bus bars runs between the spacer and the glass. As many spacers aremade of metal, e.g., stainless steel, which is conductive, it isdesirable to take steps to avoid short circuiting due to electricalcommunication between the bus bar and connector thereto and the metalspacer.

As described above, after the bus bars are connected, the electrochromiclite is integrated into an IGU, which includes, for example, wiring forthe bus bars and the like. In the embodiments described herein, both ofthe bus bars are inside the primary seal of the finished IGU. FIG. 2Ashows a cross-sectional schematic diagram of the electrochromic windowas described in relation to FIGS. 1A-C integrated into an IGU, 200. Aspacer, 205, is used to separate the electrochromic lite from a secondlite, 210. Second lite 210 in IGU 200 is a non-electrochromic lite,however, the embodiments disclosed herein are not so limited. Forexample, lite 210 can have an electrochromic device thereon and/or oneor more coatings such as low-E coatings and the like. Lite 201 can alsobe laminated glass, such as depicted in FIG. 2B (lite 201 is laminatedto reinforcing pane, 230, via resin, 235). Between spacer 205 and thefirst TCO layer of the electrochromic lite is a primary seal material,215. This primary seal material is also between spacer 205 and secondglass lite 210. Around the perimeter of spacer 205 is a secondary seal,220. Bus bar wiring/leads traverse the seals for connection to acontroller. Secondary seal 220 may be much thicker that depicted. Theseseals aid in keeping moisture out of an interior space, 225, of the IGU.They also serve to prevent argon or other gas in the interior of the IGUfrom escaping.

FIG. 3A schematically depicts an electrochromic device, 300, incross-section.

Electrochromic device 300 includes a substrate, 302, a first conductivelayer (CL), 304, an electrochromic layer (EC), 306, an ion conductinglayer (IC), 308, a counter electrode layer (CE), 310, and a secondconductive layer (CL), 314. Layers 304, 306, 308, 310, and 314 arecollectively referred to as an electrochromic stack 320. A voltagesource 316 operable to apply an electric potential across electrochromicstack 320 effects the transition of the electrochromic device from, forexample, a bleached state to a colored state (depicted). The order oflayers can be reversed with respect to the substrate.

Electrochromic devices having distinct layers as described can befabricated as all solid state devices and/or all inorganic deviceshaving low defectivity. Such devices and methods of fabricating them aredescribed in more detail in U.S. patent application, Ser. No.12/645,111, entitled, “Fabrication of Low-Defectivity ElectrochromicDevices,” filed on Dec. 22, 2009 and naming Mark Kozlowski et al. asinventors, and in U.S. patent application Ser. No. 12/645,159, entitled,“Electrochromic Devices,” filed on Dec. 22, 2009 and naming ZhongchunWang et al. as inventors, both of which are incorporated by referenceherein for all purposes. It should be understood, however, that any oneor more of the layers in the stack may contain some amount of organicmaterial. The same can be said for liquids that may be present in one ormore layers in small amounts. It should also be understood that solidstate material may be deposited or otherwise formed by processesemploying liquid components such as certain processes employing sol-gelsor chemical vapor deposition.

Additionally, it should be understood that the reference to a transitionbetween a bleached state and colored state is non-limiting and suggestsonly one example, among many, of an electrochromic transition that maybe implemented. Unless otherwise specified herein (including theforegoing discussion), whenever reference is made to a bleached-coloredtransition, the corresponding device or process encompasses otheroptical state transitions such as non-reflective-reflective,transparent-opaque, etc. Further, the term “bleached” refers to anoptically neutral state, for example, uncolored, transparent, ortranslucent. Still further, unless specified otherwise herein, the“color” of an electrochromic transition is not limited to any particularwavelength or range of wavelengths. As understood by those of skill inthe art, the choice of appropriate electrochromic and counter electrodematerials governs the relevant optical transition.

In embodiments described herein, the electrochromic device reversiblycycles between a bleached state and a colored state. In some cases, whenthe device is in a bleached state, a potential is applied to theelectrochromic stack 320 such that available ions in the stack resideprimarily in the counter electrode 310. When the potential on theelectrochromic stack is reversed, the ions are transported across theion conducting layer 308 to the electrochromic material 306 and causethe material to transition to the colored state.

Referring again to FIG. 3A, voltage source 316 may be configured tooperate in conjunction with radiant and other environmental sensors. Asdescribed herein, voltage source 316 interfaces with a device controller(not shown in this figure). Additionally, voltage source 316 mayinterface with an energy management system that controls theelectrochromic device according to various criteria such as the time ofyear, time of day, and measured environmental conditions. Such an energymanagement system, in conjunction with large area electrochromic devices(e.g., an electrochromic window), can dramatically lower the energyconsumption of a building. Any material having suitable optical,electrical, thermal, and mechanical properties may be used as substrate302. Such substrates include, for example, glass, plastic, and mirrormaterials. Suitable glasses include either clear or tinted soda limeglass, including soda lime float glass. The glass may be tempered oruntempered.

In many cases, the substrate is a glass pane sized for residentialwindow applications. The size of such glass pane can vary widelydepending on the specific needs of the residence. In other cases, thesubstrate is architectural glass. Architectural glass is typically usedin commercial buildings, but may also be used in residential buildings,and typically, though not necessarily, separates an indoor environmentfrom an outdoor environment. In certain embodiments, architectural glassis at least 20 inches by 20 inches, and can be much larger, for example,as large as about 80 inches by 120 inches. Architectural glass istypically at least about 2 mm thick, typically between about 3 mm andabout 6 mm thick. Of course, electrochromic devices are scalable tosubstrates smaller or larger than architectural glass. Further, theelectrochromic device may be provided on a mirror of any size and shape.

On top of substrate 302 is conductive layer 304. In certain embodiments,one or both of the conductive layers 304 and 314 is inorganic and/orsolid. Conductive layers 304 and 314 may be made from a number ofdifferent materials, including conductive oxides, thin metalliccoatings, conductive metal nitrides, and composite conductors.Typically, conductive layers 304 and 314 are transparent at least in therange of wavelengths where electrochromism is exhibited by theelectrochromic layer. Transparent conductive oxides include metal oxidesand metal oxides doped with one or more metals. Examples of such metaloxides and doped metal oxides include indium oxide, indium tin oxide,doped indium oxide, tin oxide, doped tin oxide, zinc oxide, aluminumzinc oxide, doped zinc oxide, ruthenium oxide, doped ruthenium oxide andthe like. Since oxides are often used for these layers, they aresometimes referred to as “transparent conductive oxide” (TCO) layers.Thin metallic coatings that are substantially transparent may also beused.

The function of the conductive layers is to spread an electric potentialprovided by voltage source 316 over surfaces of the electrochromic stack320 to interior regions of the stack, with relatively little ohmicpotential drop. The electric potential is transferred to the conductivelayers though electrical connections to the conductive layers. In someembodiments, bus bars, one in contact with conductive layer 304 and onein contact with conductive layer 314, provide the electric connectionbetween the voltage source 316 and the conductive layers 304 and 314.The conductive layers 304 and 314 may also be connected to the voltagesource 316 with other conventional means.

Overlaying conductive layer 304 is electrochromic layer 306. In someembodiments, electrochromic layer 306 is inorganic and/or solid. Theelectrochromic layer may contain any one or more of a number ofdifferent electrochromic materials, including metal oxides. Such metaloxides include tungsten oxide (WO₃), molybdenum oxide (MoO₃), niobiumoxide (Nb₂O₅), titanium oxide (TiO₂), copper oxide (CuO), iridium oxide(Ir₂O₃), chromium oxide (Cr₂O₃), manganese oxide (Mn₂O₃), vanadium oxide(V₂O₅), nickel oxide (Ni₂O₃), cobalt oxide (Co₂O₃) and the like. Duringoperation, electrochromic layer 306 transfers ions to and receives ionsfrom counter electrode layer 310 to cause optical transitions.

Generally, the colorization (or change in any optical property—e.g.,absorbance, reflectance, and transmittance) of the electrochromicmaterial is caused by reversible ion insertion into the material (e.g.,intercalation) and a corresponding injection of a charge balancingelectron. Typically some fraction of the ions responsible for theoptical transition is irreversibly bound up in the electrochromicmaterial. Some or all of the irreversibly bound ions are used tocompensate “blind charge” in the material. In most electrochromicmaterials, suitable ions include lithium ions (Li +) and hydrogen ions(H⁺) (that is, protons). In some cases, however, other ions will besuitable. In various embodiments, lithium ions are used to produce theelectrochromic phenomena. Intercalation of lithium ions into tungstenoxide (WO_(3-y)(0≦y—0.3)) causes the tungsten oxide to change fromtransparent (bleached state) to blue (colored state).

Referring again to FIG. 3A, in electrochromic stack 320, ion conductinglayer 308 is sandwiched between electrochromic layer 306 and counterelectrode layer 310. In some embodiments, counter electrode layer 310 isinorganic and/or solid. The counter electrode layer may comprise one ormore of a number of different materials that serve as a reservoir ofions when the electrochromic device is in the bleached state. During anelectrochromic transition initiated by, for example, application of anappropriate electric potential, the counter electrode layer transferssome or all of the ions it holds to the electrochromic layer, changingthe electrochromic layer to the colored state. Concurrently, in the caseof NiWO, the counter electrode layer colors with the loss of ions.

In some embodiments, suitable materials for the counter electrodecomplementary to WO₃ include nickel oxide (NiO), nickel tungsten oxide(NiWO), nickel vanadium oxide, nickel chromium oxide, nickel aluminumoxide, nickel manganese oxide, nickel magnesium oxide, chromium oxide(Cr₂O₃), manganese oxide (MnO₂), and Prussian blue.

When charge is removed from a counter electrode 310 made of nickeltungsten oxide (that is, ions are transported from counter electrode 310to electrochromic layer 306), the counter electrode layer willtransition from a transparent state to a colored state.

In the depicted electrochromic device, between electrochromic layer 306and counter electrode layer 310, there is the ion conducting layer 308.Ion conducting layer 308 serves as a medium through which ions aretransported (in the manner of an electrolyte) when the electrochromicdevice transitions between the bleached state and the colored state.Preferably, ion conducting layer 308 is highly conductive to therelevant ions for the electrochromic and the counter electrode layers,but has sufficiently low electron conductivity that negligible electrontransfer takes place during normal operation. A thin ion conductinglayer with high ionic conductivity permits fast ion conduction and hencefast switching for high performance electrochromic devices. In certainembodiments, the ion conducting layer 308 is inorganic and/or solid.

Examples of suitable ion conducting layers (for electrochromic deviceshaving a distinct IC layer) include silicates, silicon oxides, tungstenoxides, tantalum oxides, niobium oxides, and borates. These materialsmay be doped with different dopants, including lithium. Lithium dopedsilicon oxides include lithium silicon-aluminum-oxide. In someembodiments, the ion conducting layer comprises a silicate-basedstructure. In some embodiments, a silicon-aluminum-oxide (SiAlO) is usedfor the ion conducting layer 308.

Electrochromic device 300 may include one or more additional layers (notshown), such as one or more passive layers. Passive layers used toimprove certain optical properties may be included in electrochromicdevice 300. Passive layers for providing moisture or scratch resistancemay also be included in electrochromic device 300. For example, theconductive layers may be treated with anti-reflective or protectiveoxide or nitride layers. Other passive layers may serve to hermeticallyseal electrochromic device 300.

FIG. 3B is a schematic cross-section of an electrochromic device in ableached state (or transitioning to a bleached state). In accordancewith specific embodiments, an electrochromic device, 400, includes atungsten oxide electrochromic layer (EC), 406, and a nickel-tungstenoxide counter electrode layer (CE), 410. Electrochromic device 400 alsoincludes a substrate, 402, a conductive layer (CL), 404, an ionconducting layer (IC), 408, and conductive layer (CL), 414.

A power source, 416, is configured to apply a potential and/or currentto an electrochromic stack, 420, through suitable connections (e.g., busbars) to the conductive layers, 404 and 414. In some embodiments, thevoltage source is configured to apply a potential of a few volts inorder to drive a transition of the device from one optical state toanother. The polarity of the potential as shown in FIG. 3A is such thatthe ions (lithium ions in this example) primarily reside (as indicatedby the dashed arrow) in nickel-tungsten oxide counter electrode layer410.

FIG. 3C is a schematic cross-section of electrochromic device 400 shownin FIG. 3B but in a colored state (or transitioning to a colored state).In FIG. 3C, the polarity of voltage source 416 is reversed, so that theelectrochromic layer is made more negative to accept additional lithiumions, and thereby transition to the colored state. As indicated by thedashed arrow, lithium ions are transported across ion conducting layer408 to tungsten oxide electrochromic layer 406. Tungsten oxideelectrochromic layer 406 is shown in the colored state. Nickel-tungstenoxide counter electrode 410 is also shown in the colored state. Asexplained, nickel-tungsten oxide becomes progressively more opaque as itgives up (deintercalates) lithium ions. In this example, there is asynergistic effect where the transition to colored states for bothlayers 406 and 410 are additive toward reducing the amount of lighttransmitted through the stack and substrate.

As described above, an electrochromic device may include anelectrochromic (EC) electrode layer and a counter electrode (CE) layerseparated by an ionically conductive (IC) layer that is highlyconductive to ions and highly resistive to electrons. As conventionallyunderstood, the ionically conductive layer therefore prevents shortingbetween the electrochromic layer and the counter electrode layer. Theionically conductive layer allows the electrochromic and counterelectrodes to hold a charge and thereby maintain their bleached orcolored states. In electrochromic devices having distinct layers, thecomponents form a stack which includes the ion conducting layersandwiched between the electrochromic electrode layer and the counterelectrode layer. The boundaries between these three stack components aredefined by abrupt changes in composition and/or microstructure. Thus,the devices have three distinct layers with two abrupt interfaces.

In accordance with certain embodiments, the counter electrode andelectrochromic electrodes are formed immediately adjacent one another,sometimes in direct contact, without separately depositing an ionicallyconducting layer. In some embodiments, electrochromic devices having aninterfacial region rather than a distinct IC layer are employed. Suchdevices, and methods of fabricating them, are described in U.S. patentapplications Ser. Nos. 12/772,055 and 12/772,075, each filed on Apr. 30,2010, and in U.S. patent applications Ser. Nos. 12/814,277 and12/814,279, each filed on Jun. 11, 2010—each of the four applications isentitled “Electrochromic Devices,” each names Zhongchun Wang et al. asinventors, and each is incorporated by reference herein in its entirety.

WINDOW CONTROLLERS AND CONTROL ALGORITHMS

A window controller is used to control the state (i.e., bleached,neutral or some level of coloration) of the electrochromic device of anelectrochromic window. In some embodiments, the window controller isable to transition the electrochromic window between two states, ableached state and a colored state. In other embodiments, the controllercan additionally transition the electrochromic window (e.g., having asingle electrochromic device) to intermediate coloration states. Certainelectrochromic windows allow intermediate coloration levels by using twoelectrochromic lites in a single IGU, where each lite is a two-statelite. This is described in more detail below.

As noted above with respect to FIGS. 2A and 2B, in some embodiments, anelectrochromic window can include an electrochromic device on one liteof an IGU and another electrochromic device on the other lite of an IGU.If the window controller is able to transition each electrochromicdevice between two states, a bleached state and a colored state, theelectrochromic window is able to attain four different states, a coloredstate with both electrochromic devices being colored, a firstintermediate state with one electrochromic device being colored, asecond intermediate state with the other electrochromic device beingcolored, and a bleached state with both electrochromic devices beingbleached. Embodiments of multi-pane electrochromic windows are furtherdescribed in U.S. patent application Ser. No. 12/851,514, namingFriedman et al.

as inventors, titled “MULTI-PANE ELECTROCHROMIC WINDOWS” and filed onAug. 5, 2010, which is incorporated herein by reference in its entiretyand for all purposes.

In some embodiments, the window controller is able to transition anelectrochromic window having an electrochromic device capable oftransitioning between two or more states. For example, a windowcontroller may be able to transition the electrochromic window to ableached state, an intermediate state, and a colored state. In someother embodiments, the window controller is able to transition anelectrochromic window incorporating an electrochromic device between anynumber of states between the bleached state and the colored state.Embodiments of methods and controllers for transitioning anelectrochromic window to an intermediate state or states are furtherdescribed in U.S. patent application Ser. No. 13/049,623, naming Mehtaniet al. as inventors, titled “CONTROLLING TRANSITIONS IN OPTICALLYSWITCHABLE DEVICES” and filed on Mar. 16, 2011, which is incorporatedherein by reference in its entirety and for all purposes.

In some embodiments, a window controller can power one or moreelectrochromic devices in an electrochromic window. Typically, thisfunction of the window controller is augmented with one or more otherfunctions described in more detail below. Window controllers describedherein are not limited to those that have the function of powering anelectrochromic device to which it is associated for the purposes ofcontrol. That is, the power source for the electrochromic window may beseparate from the window controller, where the controller has its ownpower source and directs application of power from the window powersource to the window. However, it is convenient to include a powersource with the window controller and to configure the controller topower the window directly, because it obviates the need for separatewiring for powering the electrochromic window.

Further, the window controllers described in this section are describedas standalone controllers which may be configured to control thefunctions of a single window or a plurality of electrochromic windows,without integration of the window controller into a building controlnetwork or a building management system (BMS).

Window controllers, however, may be integrated into a building controlnetwork or a BMS, as described further in the Building Management Systemsection of this disclosure.

FIG. 4 depicts a block diagram of a window controller. FIG. 4 is asimplified block diagram of a window controller, and more detailregarding window controllers can be found in related U.S. patentapplication Ser. No. xx/xxx,xxx, naming Brown as inventor, titled“CONTROLLER FOR OPTICALLY SWITCHABLE WINDOWS” (Attorney Docket No.SLDMP041) and filed on , and in U.S. patent application Ser. No.xx/xxx,xxx, naming Brown as inventor, titled “CONTROLLER FOR DRIVINGOPTICAL TRANSITIONS IN MULTIPLE WINDOW TYPES” (Attorney Docket No.SLDMP042) and filed on , both of which are incorporated herein byreference in their entireties and for all purposes. As shown in FIG. 4,a window controller, 450, includes a microcontroller, 455, a power widthmodulator (PWM), 460, a signal conditioning module, 465, and a smartlogic module, 470.

FIG. 5 depicts a schematic diagram of a room including an electrochromicwindow and a plurality of sensors. In some embodiments, output fromthese sensors may be input to a signal conditioning module, 465, of awindow controller, 450. In some other embodiments, output from thesesensors may be input to a network including a building managementsystem, as described further below in the Building Management Systemsection. Although the various sensors are depicted as being, e.g., on avertical surface of the room, this is for the sake of simplicity, andany or all of the sensors may be on the ceiling or the floor as well.

A room, 500, includes an electrochromic window, 505. Electrochromicwindow 505 is between the exterior and the interior of a building whichincludes room 500. Window controller 450 is connected to and configuredto control the optical state of electrochromic window 505. The sensorsin room 500 include an exterior photosensor, 510, an exteriortemperature sensor, 515, an interior photosensor, 520, an interiortransmissivity sensor, 525, an occupancy sensor, 530, and a power meter,535. Each of these sensors is described briefly, below.

Exterior photosensor 510 and interior photosensor 520 are devices thatare able to detect the irradiance of light incident upon them. Lightincident upon a photosensor may be light directly from a light source orlight reflected from a surface to the photosensor.

Exterior photosensor 510 generally measures the direct or reflectedsunlight incident upon the photosensor. A light level detected byexterior photosensor 510 changes with the time of day and with the timeof year as the angle at which sunlight strikes the earth changes. Thelight level detected by exterior photosensor 510 also changes with theweather; e.g., on cloudy days, sunlight would be blocked by the cloudsand the light level detected by exterior photosensor 510 would be lowerthan on cloudless days. In some embodiments, there may be one or moreexterior photosensors 510. Output from the one or more exteriorphotosensors 510 could be compared to one another to determine, forexample, if one of exterior photosensors 510 is shaded by an object,such as by a bird that landed on exterior photosensor 510.

Interior photosensor 520 generally measures the ambient light in room500. In some embodiments, interior photosensor measures the lightreflected from a surface in the field of view of interior photosensor520. With the same lighting of room 500, interior photosensor 520 wouldmeasure a higher light level when a piece of white paper is in the fieldof view of interior photosensor 520 than when, e.g., a piece of coloredcarpet is in the field of view of interior photosensor 520, for example,due to the higher reflectivity of the white paper. Because of this, ifinterior photosensor 520 is moved or if the object(s) in the field ofview of interior photosensor 520 is changed, the output of interiorphotosensor 520 may change. Thus, in some embodiments, window controller450 may perform a recalibration routine to determine the output range ofinterior photosensor 520, which again depends on the object(s) in thefield of view interior photosensor 520. Such a recalibration routine maybe performed according to set schedule (e.g., once a week) or triggeredby a person (e.g., a maintenance person who rearranges the furniture inroom 500).

Exterior photosensor 510 and interior photosensor 520 may be any numberof different types of photosensors. For example, exterior photosensor510 and interior photosensor 520 can be charge coupled devices (CCDs),photodiodes, photoresistors, or photovoltaic cells. One of ordinaryskill in the art would appreciate that future developments inphotosensor technology would also work, as they measure light intensityand provide an electrical output representative of the light level.Exterior temperature sensor 515 is a device able to measure the outsidetemperature. Exterior temperature sensor 515 can be any number ofdifferent temperature sensors, including a thermocouple, a thermistor,or a resistance temperature detector. In some embodiments, room 500further includes an interior temperature sensor.

Interior transmissivity sensor 525 is a device able to measure theamount of light transmitted though electrochromic window 505. In someembodiments, interior transmissivity sensor 525 is a photosensor, whichmay be similar to exterior photosensor 510 or interior photosensor 520,with the field of view of the sensor oriented to be facingelectrochromic window 505 in order to measure incident light passingthrough electrochromic window 505. By combining the measurement ofexterior photosensor 510 with a photosensor having a field of viewfacing the interior of electrochromic window 505, the transmissivity ofelectrochromic window 505 can be determined.

Occupancy sensor 530 is a device able to detect when a person is in room500. Occupancy sensors are usually motion sensors; when occupancy sensor530 detects motion, it is assumed that a person in in room 500, and whenoccupancy sensor 530 does not detect motion, it is assumed that a personin not in room 500. Occupancy sensors may be set so that it is assumedthat a person is in a room for a period of time after the last motionwas detected; this can account for a person sitting at a desk and notmoving very much, but still being in the room. In some embodiments, theoccupancy sensor may be a motion sensor used to control the lightslighting the room. Occupancy sensor 530 can use, for example, infrared(IR) technology, acoustic technology, or a combination of the two. Thefield of view of occupancy sensor 530 may be selected/adjusted so thatit responds to motion in room 500 and not to motion outside of room 500(e.g., motion outside of the building housing room 500 or motion in ahallway of the building housing room 500). Power meter 535 is a deviceable to measure the power consumption of room 500.

The power consumption of room 500 may include heating, ventilation, andair conditioning systems (HVAV systems) and lighting. In someembodiments, power meter 535 includes devices able to interface with thewires of the circuits providing power to room 500. Power meter may beable to separately measure the power consumed by the interior lightingof room 500 and the power consumed by HVAC system of room 500 if theinterior lighting and HVAC system are on different circuits of room 500.

In some embodiments, when window controller 450 is not connected to anetwork, two or more sensors may provide output signals to windowcontroller 450 through signal conditioning module 465. Signalconditioning module 465 passes these output signals to amicrocontroller, 455. Microcontroller 455 determines the level of tintof electrochromic window 505, based on the outputs, and instructs a PWM,460, to apply a voltage and/or current to electrochromic window 505 totransition to the desired state.

In some embodiments, output from exterior photosensor 510, interiorphotosensor 520, a temperature sensor, and a tint command are input tosignal conditioning module 465. The temperature sensor may be aninterior temperature sensor (not shown) or exterior temperature sensor515. The tint command may be a command from a person or occupant in room500 as to the tint level desired by the person. For example, dependingon electrochromic window 505, the person may instruct the window totransition to a bleached state, a colored state, or an intermediatestate. Such tint command instructions may be made, for example, with awireless remote or with a panel associated with window controller 450.If room 500 is a bedroom, for example, the person may wantelectrochromic window 505 to be in a colored state at night for privacy.

In some embodiments, the tint command input may be a voltage signal tosignal conditioning module 465 of about 0 V to about 10 V. A tintcommand input of 0 V to 4.9 V may indicate a command for electrochromicwindow 505 to transition to a beached state and a tint command input of5 V to about 10 V may indicate a command for electrochromic window 505to transition to a colored state. As another example, when theelectrochromic window 505 has four states, a tint command input of 0 Vto 2.5 V may indicate a command for electrochromic window 505 totransition to a beached state, a tint command input of 2.6 V to 5 V mayindicate a command for electrochromic window 505 to transition to afirst intermediate state, a tint command input of 5.1 V to 7.5 V mayindicate a command for electrochromic window 505 to transition to asecond intermediate state, and a tint command input of 7.6 V to about 10V may indicate a command for electrochromic window 505 to transition toa colored state.

The output signals from the sensors and the tint command are passed tomicrocontroller 455. Whether or not electrochromic window 505transitions to a state as indicated by the tint command will depend onhow microcontroller 455 is configured to process outputs from exteriorphotosensor 510, interior photosensor 520, and the temperature sensor,in relation to the tint command. For example, in some embodiments, thetint command input may override the output from exterior photosensor510, interior photosensor 520, and the temperature sensor andelectrochromic window 505 may transition to a state indicated by thetint command input. Microcontroller 455 instructs PWM 460 to supplycurrent and/or voltage to transition electrochromic window 505 accordingto the tint command input.

In some embodiments, microcontroller 455 may employ any one or more ofvarious logic functions or algorithms to arrive at tint decisions basedon signals from the sensors and/or other input. The sensor outputs mayserve as independent variables to a linear or non-linear expression, alook up table, a tree, etc. In some embodiments, microcontroller 455uses a function to determine the current and/or voltage that power widthmodulator 460 should send to electrochromic window 505. An example ofone function is shown in FIG. 6.

FIG. 6 depicts a function that uses weighting constants, k₁, k₂, k₃, andk₄ to weight the outputs from the different sensors/commands, where EPis the exterior photosensor output, IP is the interior photosensoroutput, T is the temperature sensor output, and TC is the tint commandinput. The weighting constants are set to achieve the desired responsefor electrochromic window 505. Using the function, an output value (OV)is determined. Depending on the output value, the microcontroller 455can instruct PWM 460 to transition electrochromic window 505 to adesired state.

For example, when the output value ranges from 0 to 15 (e.g., 16 tintstates, ranging from about 67% transmissivity to 4% transmissivity) andelectrochromic window 505 has two states, with an output value of 0,window controller 450 can instruct electrochromic window 505 totransition to a bleached state, and with an output value of 15, windowcontroller 450 can instruct electrochromic window 505 to transition to acolored state. As another example, when the output value ranges from 0to 15 and electrochromic window 505 has four states, with an outputvalue of 0 to 4, window controller 450 can instruct electrochromicwindow 505 to transition to a bleached state, with an output value of 5to 9, window controller 450 can instruct electrochromic window 505 totransition to a first intermediate state, with an output value of 10 to14, window controller 450 can instruct electrochromic window 505 totransition to a second intermediate state, and with an output value of15, window controller 450 can instruct electrochromic window 505 totransition to a colored state. As yet another example, when the outputvalue ranges from 0 to 15 and electrochromic window 505 has an infinitenumber of intermediate states, with an output value of 0, windowcontroller 450 can instruct electrochromic window 505 to transition to ableached state, with an output value of 15, window controller 450 caninstruct electrochromic window 505 to transition to a colored state, andwith an output value between 0 to 15, window controller 450 can instructelectrochromic window 505 to transition to a tint level corresponding tothe output value.

The weighting constants, k₁, k₂, k₃, and k₄ are set to achieve thedesired response for electrochromic window 505. For example, if anoccupant in the room is to have control over the tint level ofelectrochromic window 505, the weighting constants are set to k₁=0,k₂=0, k₃=0, and k₄=1. Weighting constant k₃ (i.e., for the exteriortemperature sensor output) may be given a large value if electrochromicwindow 505 is used to reduce HVAC energy consumption in room 500.Weighting constants k₁ and k₂ (i.e., for the exterior photosensor outputand the interior photosensor output, respectively) may be given valuesto keep the lighting in room 500 relatively constant. The weightingconstants may be set to achieve any of a number of different responsesfor electrochromic window 505.

In some embodiments, weighting constants, k₁, k₂, k₃, and k₄ may changeaccording to an external influence or a schedule. Examples of externalinfluences that may cause the constants to vary include changes in theweather and changes in the power consumption conditions within abuilding or across a geographic area (which may be noted by acommunication from a power utility company). In some embodiments, theschedule may be a daily schedule, and in some other embodiments, theschedule may be a yearly schedule. In some embodiments, the schedule maybe a schedule that includes different daily schedules for differenttimes of the year. For example, the daily schedule may change for thedifferent seasons of the year, i.e., winter, spring, summer, and fall.

An example of one schedule is shown in FIG. 7. For example, schedule 1may be a schedule for 10 pm to 6 am, schedule 2 may be a schedule for 10am to 1 pm, and schedule 3 may be a schedule for 1 pm to 10 pm. Whenroom 500 is a room in a residential home, schedule 1 may colorelectrochromic window 505 for privacy, and schedules 2 and 3 may balancethe light in room 500 and the temperature.

As another example, schedule 1 may be a schedule for the winter,schedule 2 may be a schedule for the spring and the summer, and schedule3 may be a schedule for the fall. Schedules 1, 2, and 3 may balance thelight and the temperature in room 500, taking into account the differentseasons, including, for example, concomitant changes in averagetemperature, angle and location of the sun, precipitation patterns, andthe like.

FIGS. 6 and 7 show one embodiment of a relationship for determining thetint level that window controller 450 may use. More outputs fromdifferent sensors can be input to signal conditioning module 465 and thefunction and weighting constants of the function may be adjustedappropriately. Also, fewer outputs can be input to signal conditioningmodule 465. In some other embodiments, the relationship used fordetermining a level of tint is a lookup table in which levels of tintare specified for various combinations of output signal values.

FIG. 8 shows a flow chart of a method for limiting the energyconsumption in a room having at least one tintable window between aninterior and exterior of the room. The level of tinting may becontrolled automatically; i.e., output from the sensors may be input tothe window controller, and the window controller may control the tintstate of the tintable window according to the output from the sensors.

As shown in FIG. 8, in operation 805, output signals from any two ormore sensors are received. In some embodiments, output from the sensorsis received by a window controller. In some other embodiments, outputfrom these sensors is received at a network including a buildingmanagement system or a master network controller. Again, buildingmanagement systems are described further below in the BuildingManagement System section. The sensors may be selected from the groupconsisting of an exterior photosensor, an interior photosensor, anoccupancy sensor, an exterior temperature sensor, and a transmissivitysensor which detects light passing through the tintable window from theexterior. In some embodiments, when the interior photosensor is facingthe tintable window, output from both the exterior photosensor and theinterior photosensor can be used to determine the light passing throughthe tintable window from the exterior.

In some embodiments, output indicating an energy or power consumption bya heating system, a cooling system, and/or lighting in the room also isreceived. In some embodiments, devices that interface with the wires ofthe circuits providing power to the room including the tintable windowprovide the energy or power consumption output.

In operation 810, a level of tint for the tintable window is determinedusing a relationship between the received energy output signals and thelevel of tint. In some embodiments, the relationship tends to minimizeenergy consumption by a heating system, a cooling system, and/orlighting in the room while providing conditions suitable for occupancyof the room. For example, when output indicating an energy or powerconsumption by a heating system, a cooling system, and/or lighting inthe room is received, this output may be used with the other receivedoutput signals in to determine the level of tinting for the tintablewindow to minimize energy consumption.

In some embodiments, the relationship is an expression in which thelevel of tint is the dependent variable and the output signals areindependent variables; an example of such a relationship is shown inFIG. 6. The window controller receives the output signals and computesthe level of tint based on the relationship and the output signals. Insome other embodiments, the relationship is a lookup table in whichlevels of tint are specified for various combinations of output signalvalues. Such a lookup table may be used, for example, when the tintablewindow is capable of achieving a finite number of states (e.g., twostates, bleached and colored, or four states).

In some embodiments of method 800, the output signals include a signalfrom an exterior photosensor. The relationship employed in operation 810requires transitioning from a first darker tint level to a secondlighter tint level when the output signal from the exterior photosensorpasses a first threshold. The relationship employed in operation 810also requires transitioning from the second lighter tint level to thefirst darker tint level when the output signal from the exteriorphotosensor passes a second threshold. These embodiments are describedfurther below with respect to FIGS. 9 and 10.

Referring again to FIG. 8, in operation 815, instructions are providedto change the tint of the tintable window to the level of tintdetermined in operation 810. In some embodiments, this includes a windowcontroller applying voltage or current to the tintable window to drivethe change in tint pursuant to the instructions. For example, for windowcontroller 450 shown in FIG. 4, microcontroller 455 provides instructionto PWM 460 to apply voltage and/or current to the tintable window.

Method 800 can be implemented in an iterative process, as described inoperation 820, a decision block. For example, as part of an automatedprogram to control one or more electrochromic windows, the tint levelinstructions may be generated based on a preset timing function, whereafter a preset time has elapsed, the controller samples output from thesensors in order to generate new instructions for the window. If thetime period has not elapsed, then no further instructions are needed andthe method ends. Once the time period has elapsed, then operations 805through 815 are repeated. Decision block 820 may also be based on anynumber of criteria, depending on the desired control level of the one ormore windows. For example, decision block 820 may query whether therehas been any change in the output from one or more sensors. If theanswer is negative, then the method is complete; if the answer isaffirmative, then operations 805 through 815 are repeated.

FIG. 9 shows a flow chart of a method, 900, of operating a tintablewindow installed between an interior and exterior of a room. The levelof tinting may be controlled automatically; i.e., output from thesensors may be input to the window controller, and the window controllermay control the tint state of the tintable window according to theoutput from the sensors.

In operation 905 of method 900 shown in FIG. 9, signals indicating alevel of exterior irradiance received at or proximate to the tintablewindow are received. The exterior photosensor measures the amount oflight incident upon the photosensor, or the irradiance. Illuminance isclosely related to irradiance; illuminance is a measure of the intensityof illumination on a surface. Irradiance, however, is based on physicalpower, with all wavelengths being weighted equally, while illuminancetakes into account that the human eye's visual system is more sensitiveto some wavelengths than others, and accordingly every wavelength isgiven a different weight. FIG. 10 shows a plot of illuminance versustime for a 24-hour period, with the time starting at 0 (i.e., 12 AM) andending 24 hours later. As shown, the illuminance is low at 0, thenincreases with time until about midday, reaching a maximum at midday,and then decreases throughout the remainder of the day.

In operation 910, a level of tint for the tintable window is determinedusing a relationship between the received output signals and the levelof tint. The relationship employed in operation 910 requirestransitioning from a first lighter tint level to a second darker tintlevel when the output signal from the exterior photosensor passes afirst threshold, 1005. The relationship employed in operation 910 alsorequires transitioning from the second darker tint level to the firstlighter tint level when the output signal from the exterior photosensorpasses a second threshold, 1010. First threshold 1005 and secondthreshold 1010 are different levels of irradiance/illuminance. Forexample, in some embodiments, the level of irradiance/illuminance atsecond threshold 1010 is lower than the level of irradiance/illuminanceat first threshold 1005.

In operation 915, instructions are provided to change the tint of thetintable window to the level of tint determined in operation 910. Insome embodiments, operation 915 is similar to operation 815 describedwith respect to FIG. 8.

Method 900 of controlling the tint state of a tintable window maymaximize energy savings for the room including the tintable window. Forexample, the room may be lit by sunlight in the early morning,minimizing lighting energy. As the sun's position changes andtemperature in the room starts to increase due to sunlight though thetintable window, the HVAC power used for cooling the room increases, andthe tintable window is transitioned at first threshold 1005. Then, whenthe sun begins to set and the sunlight though the tintable windowdecreases the HVAC power used for cooling, the tintable window istransitioned at second threshold 1010, which may reduce the lightingenergy.

Analogous to method 800, method 900 may include a decision block as inmethod 800. For example, the decision to repeat operations 905-915 maybe based on a preset timing event; for example, knowing the expectedillumination during a 24 hour period, the illumination is sampledaccording to a preset schedule. In another example, if a change inillumination level as read by the photosensor meets a certain thresholdvalue, then new tint instructions are generated and provided to thewindow(s) based on this change in illumination.

The methods shown in FIGS. 8 and 9 are two methods of controlling thetint state of a tintable window. Many other methods of controlling thetint state of a tintable window are possible, using differentcombinations of sensors and weighting the output of the differentsensors using weighting functions.

BUILDING MANAGEMENT SYSTEMS

The window controllers described herein also are suited for integrationwith a BMS. A BMS is a computer-based control system installed in abuilding that monitors and controls the building's mechanical andelectrical equipment such as ventilation, lighting, power systems,elevators, fire systems, and security systems. A BMS consists ofhardware, including interconnections by communication channels to acomputer or computers, and associated software for maintainingconditions in the building according to preferences set by the occupantsand/or by the building manager. For example, a BMS may be implementedusing a local area network, such as Ethernet. The software can be basedon, for example, internet protocols and/or open standards. One exampleof software is software from Tridium, Inc. (of Richmond, Virginia). Onecommunications protocol commonly used with a BMS is BACnet (buildingautomation and control networks).

A BMS is most common in a large building, and typically functions atleast to control the environment within the building. For example, a BMSmay control temperature, carbon dioxide levels, and humidity within abuilding. Typically, there are many mechanical devices that arecontrolled by a BMS such as heaters, air conditioners, blowers, vents,and the like. To control the building environment, a BMS may turn on andoff these various devices under defined conditions. A core function of atypical modern BMS is to maintain a comfortable environment for thebuilding's occupants while minimizing heating and cooling costs/demand.Thus, a modern BMS is used not only to monitor and control, but also tooptimize the synergy between various systems, for example, to conserveenergy and lower building operation costs. In some embodiments, a windowcontroller is integrated with a BMS, where the window controller isconfigured to control one or more tintable or electrochromic windows. Inone embodiment, the one or more electrochromic windows include at leastone all solid state and inorganic electrochromic device. In oneembodiment, the one or more electrochromic windows include only allsolid state and inorganic windows. In one embodiment, the electrochromicwindows are multistate electrochromic windows, as described in U.S.patent application Ser. No. 12/851,514, filed on Aug. 5, 2010, andentitled “Multipane Electrochromic Windows.”

FIG. 11 depicts a schematic diagram of an embodiment of a BMS, 1100,that manages a number of systems of a building, 1101, including securitysystems, heating/ventilation/air conditioning (HVAC), lighting of thebuilding, power systems, elevators, fire systems, and the like. Securitysystems may include magnetic card access, turnstiles, solenoid drivendoor locks, surveillance cameras, burglar alarms, metal detectors, andthe like. Fire systems may include fire alarms and fire suppressionsystems including a water plumbing control. Lighting systems may includeinterior lighting, exterior lighting, emergency warning lights,emergency exit signs, and emergency floor egress lighting. Power systemsmay include the main power, backup power generators, and uninterruptedpower source (UPS) grids.

Also, BMS 1100 manages a window controller, 1102. In this example,window controller 1102 is depicted as a distributed network of windowcontrollers including a master network controller, 1103, intermediatenetwork controllers, 1105 a and 1105 b, and end or leaf controllers,1110. End or leaf controllers 1110 may be similar to window controller450 described with respect to FIG. 4. For example, master networkcontroller 1103 may be in proximity to the BMS, and each floor ofbuilding 1101 may have one or more intermediate network controllers 1105a and 1105 b, while each window of the building has its own endcontroller 1110. In this example, each of controllers 1110 controls aspecific electrochromic window of building 1101.

Each of controllers 1110 can be in a separate location from theelectrochromic window that it controls, or be integrated into theelectrochromic window. For simplicity, only ten electrochromic windowsof building 1101 are depicted as controlled by window controller 1102.In a typical setting there may be a large number of electrochromicwindows in a building controlled by window controller 1102. Windowcontroller 1102 need not be a distributed network of window controllers.For example, a single end controller which controls the functions of asingle electrochromic window also falls within the scope of theembodiments disclosed herein, as described above. Advantages andfeatures of incorporating electrochromic window controllers as describedherein with BMS's are described below in more detail and in relation toFIG. 11, where appropriate.

One aspect of the disclosed embodiments is a BMS including amultipurpose electrochromic window controller as described herein. Byincorporating feedback from a electrochromic window controller, a BMScan provide, for example, enhanced: 1) environmental control, 2) energysavings, 3) security, 4) flexibility in control options, 5) improvedreliability and usable life of other systems due to less reliancethereon and therefore less maintenance thereof, 6) informationavailability and diagnostics, 7) effective use of staff, and variouscombinations of these, because the electrochromic windows can beautomatically controlled.

In some embodiments, a BMS may not be present or a BMS may be presentbut may not communicate with a master network controller or communicateat a high level with a master network controller. In some embodiments, amaster network controller can provide, for example, enhanced: 1)environmental control, 2) energy savings, 3) flexibility in controloptions, 4) improved reliability and usable life of other systems due toless reliance thereon and therefore less maintenance thereof, 5)information availability and diagnostics, 6) effective use of staff, andvarious combinations of these, because the electrochromic windows can beautomatically controlled. In these embodiments, maintenance on the BMSwould not interrupt control of the electrochromic windows.

FIG. 12 depicts a block diagram of an embodiment of a building network,1200, for a building. As noted above, network 1200 may employ any numberof different communication protocols, including BACnet. As shown,building network 1200 includes a master network controller, 1205, alighting control panel, 1210, a building management system (BMS), 1215,a security control system, 1220, and a user console, 1225. Thesedifferent controllers and systems in the building may be used to receiveinput from and/or control a HVAC system, 1230, lights, 1235, securitysensors, 1240, door locks, 1245, cameras, 1250, and tintable windows,1255, of the building.

Master network controller 1205 may function in a similar manner asmaster network controller 1103 described with respect to FIG. 11.Lighting control panel 1210 may include circuits to control the interiorlighting, the exterior lighting, the emergency warning lights, theemergency exit signs, and the emergency floor egress lighting. Lightingcontrol panel 1210 also may include occupancy sensors in the rooms ofthe building. BMS 1215 may include a computer server that receives datafrom and issues commands to the other systems and controllers of network1200. For example, BMS 1215 may receive data from and issue commands toeach of the master network controller 1205, lighting control panel 1210,and security control system 1220. Security control system 1220 mayinclude magnetic card access, turnstiles, solenoid driven door locks,surveillance cameras, burglar alarms, metal detectors, and the like.User console 1225 may be a computer terminal that can be used by thebuilding manager to schedule operations of, control, monitor, optimize,and troubleshoot the different systems of the building. Software fromTridium, Inc., may generate visual representations of data fromdifferent systems for user console 1225.

Each of the different controls may control individual devices/apparatus.Master network controller 1205 controls windows 1255. Lighting controlpanel 1210 controls lights 1235. BMS 1215 may control HVAC 1230.Security control system 1220 controls security sensors 1240, door locks1245, and cameras 1250. Data may be exchanged and/or shared between allof the different devices/apparatus and controllers that are part ofbuilding network 1200.

In some cases, the systems of BMS 1100 or building network 1200 may runaccording to daily, monthly, quarterly, or yearly schedules. Forexample, the lighting control system, the window control system, theHVAC, and the security system may operate on a 24 hour scheduleaccounting for when people are in the building during the work day. Atnight, the building may enter an energy savings mode, and during theday, the systems may operate in a manner that minimizes the energyconsumption of the building while providing for occupant comfort. Asanother example, the systems may shut down or enter an energy savingsmode over a holiday period.

The scheduling information may be combined with geographicalinformation. Geographical information may include the latitude andlongitude of the building. Geographical information also may includeinformation about the direction that each side of the building faces.Using such information, different rooms on different sides of thebuilding may be controlled in different manners. For example, for eastfacing rooms of the building in the winter, the window controller mayinstruct the windows to have no tint in the morning so that the roomwarms up due to sunlight shining in the room and the lighting controlpanel may instruct the lights to be dim because of the lighting from thesunlight. The west facing windows may be controllable by the occupantsof the room in the morning because the tint of the windows on the westside may have no impact on energy savings. However, the modes ofoperation of the east facing windows and the west facing windows mayswitch in the evening (e.g., when the sun is setting, the west facingwindows are not tinted to allow sunlight in for both heat and lighting).

Described below is an example of a building, for example, like building1101 in FIG. 11, including a building network or a BMS, tintable windowsfor the exterior windows of the building (i.e., windows separating theinterior of the building from the exterior of the building), and anumber of different sensors. Light from exterior windows of a buildinggenerally has an effect on the interior lighting in the building about20 feet or about 30 feet from the windows. That is, space in a buildingthat is more that about 20 feet or about 30 feet from an exterior windowreceives little light from the exterior window. Such spaces away fromexterior windows in a building are lit by lighting systems of thebuilding.

Further, the temperature within a building may be influenced by exteriorlight and/or the exterior temperature. For example, on a cold day andwith the building being heated by a heating system, rooms closer todoors and/or windows will lose heat faster than the interior regions ofthe building and be cooler compared to the interior regions.

For exterior photosensors, the building may include exteriorphotosensors on the roof of the building. Alternatively, the buildingmay include an exterior photosensor associated with each exterior window(e.g., as described in relation to FIG. 5, room 500) or an exteriorphotosensor on each side of the building. An exterior photosensor oneach side of the building could track the irradiance/illuminance on aside of the building as the sun changes position throughout the day.

For exterior temperature sensors, the building may include exteriortemperature sensors at a few locations to determine an average exteriortemperature. For interior temperature sensors, each room that has anexterior window may include an interior temperature sensor.Alternatively, a few rooms on each side of the building may include aninterior temperature sensor.

For interior photosensors and transmissivity sensors, the building mayinclude interior photosensors and interior transmissivity sensors ineach room that has an exterior window. Alternatively, a few rooms oneach side of the building may include these sensors.

Each room of the building may include an occupancy sensor that isassociated with the lights and/or lighting panel in the room. Thebuilding may include power meters for individual rooms or groups ofrooms (e.g., a group of rooms having exterior windows on one side of thebuilding). A power meter setup will depend on the circuitry setup of thebuilding, however.

Regarding the methods described with respect to FIGS. 8 and 9, when awindow controller is integrated into a building network or a BMS,outputs from sensors may be input to a network of BMS and provided asinput to the window controller. For example, in some embodiments, outputsignals from any two or more sensors are received. In some embodiments,only one output signal is received, and in some other embodiments,three, four, five, or more outputs are received. These output signalsmay be received over a building network or a BMS.

A level of tint for the tintable window is determined using arelationship between the received output signals and the level of tint.In some embodiments, determining the level of tint includes usingscheduling information for the building. For example, in someembodiments, the scheduling information includes time of year and/ortime of day information for the building. In some embodiments, thescheduling information further includes information about thegeographical facing direction of the tintable window and the latitude ofthe building. The lookup table used to determine the level of tint ofthe windows or the weighting constants used in a relationship used todetermine the level of tint of the windows may change according to theschedule.

The window controllers and the methods of controlling the tint state ofa tintable window described herein may employ different sensors orcombinations of sensors. Different sensors or combinations of sensorsmay be referred to as different “sensor setups” or “levels.” Forexample, use of an exterior photosensor may be referred to as “level 0,”use of an exterior photosensor and an interior photosensor may bereferred to as “level 1,” use of an exterior photosensor, an interiorphotosensor, and an occupancy sensor may be referred to as “level 2,”and use of an exterior photosensor, an interior photosensor, anoccupancy sensor, and a signal indicating energy or power consumption bya heating system, a cooling system, and/or lighting within the building(described below) may be referred to as “level 3.” Embodiments of eachof these different levels are described further, below.

In some embodiments, the output signals include a signal from anexterior photosensor (i.e., level 0). The relationship employed todetermine the level of tint may include an expression or look up tablein which the level of tint is the dependent variable and the signal fromthe exterior photosensor is the independent variable. In someembodiments, the relationship employed in operation 810 uses schedulinginformation including time of year and/or time of day information forthe building. For example, a different relationship over a 24 hour daymay be used for each calendar day of the year.

In some embodiments, the output signals include a signal from anexterior photosensor and a signal from an interior photosensor (i.e.,level 1). The relationship employed to determine the level of tint mayinclude an expression or look up table in which the level of tint is thedependent variable and the signals from the exterior photosensor and theinterior photosensor are independent variables. In some embodiments, therelationship employed in operation 810 uses scheduling informationincluding time of year and/or time of day information for the building.For example, a different relationship over a 24 hour day may be used foreach calendar day of the year.

In some embodiments, the output signals received include a signal froman exterior photosensor, a signal from an interior photosensor, and asignal from an occupancy sensor (i.e., level 2). The relationshipemployed to determine the level of tint may include an expression orlook up table in which the level of tint is the dependent variable andthe signals from the exterior photosensor, the interior photosensor, andthe occupancy sensor are independent variables. In some embodiments,when the occupancy sensor indicates that the room is not occupied, theroom may enter into a maximum energy savings mode.

In some embodiments, the output signals received include a signalindicating energy or power consumption by a heating system, a coolingsystem, and/or lighting within the building. For example, the energy orpower consumption of the heating system, the cooling system, and/or thelighting of the building may be monitored to provide the signalindicating energy or power consumption. Devices may be interfaced withor attached to the circuits and/or wiring of the building to enable thismonitoring.

Alternatively, the power systems in the building may be installed suchthat the power consumed by the heating system, a cooling system, and/orlighting for an individual room within the building or a group of roomswithin the building can be monitored.

For example, with respect to lighting in the building, a signalindicating the energy or power consumption of a light, group of lights,or a lighting system within the building is received. The light, thegroup of lights, or the lighting system may include at least one lightwithin about 20 feet or about 30 feet of a tintable window, in an areawhere changing the tint of the window can influence the lighting in thearea.

As another example, with respect to the heating and/or cooling in thebuilding, a signal indicating the energy or power consumption of aheating or cooling device providing temperature control within thebuilding is received. The heating or cooling device may be heating orcooling an area of the building within about 50 feet of a tintablewindow.

In some embodiments, the output signals received include a signal froman exterior photosensor, a signal from an interior photosensor, a signalfrom an occupancy sensor, and an energy or power consumption signal(i.e., level 3). The energy or power consumption signal indicates energyor power consumption by a heating system, a cooling system, and/orlighting in the building or by room in the building. The relationshipemployed to determine the level of tint reduces energy consumption by aheating system, a cooling system, and/or lighting in the building whileproviding conditions suitable for occupancy of the building.

Instructions are then provided to change the tint of the tintable windowto the determined level of tint. For example, referring to FIG. 11, thismay include master network controller 1103 issuing commands to one ormore intermediate network controllers 1105 a and 1105 b, which in turnissue commands to end controllers 1110 that control each window of thebuilding. End controllers 1100 may apply voltage and/or current to thewindow to drive the change in tint pursuant to the instructions.

In some embodiments, a building including electrochromic windows and aBMS may be enrolled in or participate in a program run by the utility orutilities providing power to the building. The program may be a programin which the energy consumption of the building is reduced when a peakload occurrence is expected. The utility may send out a warning signalprior to an expected peak load occurrence. For example, the warning maybe sent on the day before, the morning of, or about one hour before theexpected peak load occurrence. A peak load occurrence may be expected tooccur on a hot summer day when cooling systems/air conditioners aredrawing a large amount of power from the utility, for example. Thewarning signal may be received by the BMS of the building or by windowcontrollers configured to control the electrochromic windows in thebuilding. The BMS can then instruct the window controller(s) totransition the appropriate electrochromic windows to a colored state toaid in reducing the power draw of the cooling systems in the building atthe time when the peak load is expected.

In some embodiments, tintable windows for the exterior windows of thebuilding (i.e., windows separating the interior of the building from theexterior of the building), may be grouped in zones, with tintablewindows in a zone being instructed in a similar manner. For example,groups of electrochromic windows on different floors of the building ordifferent sides of the building may be in different zones. For example,on the first floor of the building, all of the east facingelectrochromic windows may be in zone 1, all of the south facingelectrochromic windows may be in zone 2, all of the west facingelectrochromic windows may be in zone 3, and all of the north facingelectrochromic windows may be in zone 4. As another example, all of theelectrochromic windows on the first floor of the building may be in zone1, all of the electrochromic windows on the second floor may be in zone2, and all of the electrochromic windows on the third floor may be inzone 3. As yet another example, all of the east facing electrochromicwindows may be in zone 1, all of the south facing electrochromic windowsmay be in zone 2, all of the west facing electrochromic windows may bein zone 3, and all of the north facing electrochromic windows may be inzone 4. As yet another example, east facing electrochromic windows onone floor could be divided into different zones. Any number of tintablewindows on the same side and/or different sides and/or different floorsof the building may be assigned to a zone.

In some embodiments, electrochromic windows in a zone may be controlledby the same window controller. In some other embodiments, electrochromicwindows in a zone may be controlled by different window controllers, butthe window controllers may all receive the same output signals fromsensors and use the same function or lookup table to determine the levelof tint for the windows in a zone.

In some embodiments, electrochromic windows in a zone may be controlledby a window controller or controllers that receive an output signal froma transmissivity sensor. In some embodiments, the transmissivity sensormay be mounted proximate the windows in a zone. For example, thetransmissivity sensor may be mounted in or on a frame containing an IGU(e.g., mounted in or on a mullion, the horizontal sash of a frame)included in the zone. In some other embodiments, electrochromic windowsin a zone that includes the windows on a single side of the building maybe controlled by a window controller or controllers that receive anoutput signal from a transmissivity sensor.

In some embodiments, a transmissivity sensor may provide an outputsignal to a window controller to control the electrochromic windows of afirst zone (e.g., a master control zone). The window controller may alsocontrol the electrochromic windows in a second zone (e.g., a slavecontrol zone) in the same manner as the first zone. In some otherembodiments, another window controller may control the electrochromicwindows in the second zone in the same manner as the first zone.

In some embodiments, a building manager, occupants of rooms in thesecond zone, or other person may manually instruct (using a tint orclear command or a command from a user console of a BMS, for example)the electrochromic windows in the second zone (i.e., the slave controlzone) to enter a tint state or a clear state. In some embodiments, whenthe tint state of the windows in the second zone is overridden with sucha manual command, the electrochromic windows in the first zone (i.e.,the master control zone) remain under control of the window controllerreceiving output from the transmissivity sensor. The second zone mayremain in a manual command mode for a period of time and then revertback to be under control of the window controller receiving output fromthe transmissivity sensor. For example, the second zone may stay in amanual mode for one hour after receiving an override command, and thenmay revert back to be under control of the window controller receivingoutput from the transmissivity sensor.

In some embodiments, a building manager, occupants of rooms in the firstzone, or other person may manually instruct (using a tint command or acommand from a user console of a BMS, for example) the electrochromicwindows in the first zone (i.e., the master control zone) to enter atint state or a clear state. In some embodiments, when the tint state ofthe windows in the first zone is overridden with such a manual command,the electrochromic windows in the second zone (i.e., the slave controlzone) remain under control of the window controller receiving outputsfrom the exterior photosensor. The first zone may remain in a manualcommand mode for a period of time and then revert back to be undercontrol of window controller receiving output from the transmissivitysensor. For example, the first zone may stay in a manual mode for onehour after receiving an override command, and then may revert back to beunder control of the window controller receiving output from thetransmissivity sensor. In some other embodiments, the electrochromicwindows in the second zone may remain in the tint state that they are inwhen the manual override for the first zone is received. The first zonemay remain in a manual command mode for a period of time and then boththe first zone and the second zone may revert back to be under controlof the window controller receiving output from the transmissivitysensor.

Any of the methods described herein of control of a tintable window,regardless of whether the window controller is a standalone windowcontroller or is interfaced with a building network, may be used controlthe tint of a tintable window.

WIRELESS OR WIRED COMMUNICATION

In some embodiments, window controllers described herein includecomponents for wired or wireless communication between the windowcontroller, sensors, and separate communication nodes. Wireless or wiredcommunications may be accomplished with a communication interface thatinterfaces directly with the window controller. Such interface could benative to the microprocessor or provided via additional circuitryenabling these functions.

A separate communication node for wireless communications can be, forexample, another wireless window controller, an end, intermediate, ormaster window controller, a remote control device, or a BMS. Wirelesscommunication is used in the window controller for at least one of thefollowing operations: programming and/or operating the EC window,collecting data from the EC window from the various sensors andprotocols described herein, and using the EC window as a relay point forwireless communication. Data collected from EC windows also may includecount data such as number of times an EC device has been activated,efficiency of the EC device over time, and the like. These wirelesscommunication features is described in more detail below. In oneembodiment, wireless communication is used to operate the associatedelectrochromic windows, for example, via an infrared (IR), and/or radiofrequency (RF) signal. In certain embodiments, the controller willinclude a wireless protocol chip, such as Bluetooth, EnOcean, WiFi,Zigbee, and the like. Window controllers may also have wirelesscommunication via a network. Input to the window controller can bemanually input by a user, either directly or via wireless communication,or the input can be from a BMS of a building of which the electrochromicwindow is a component.

In one embodiment, when the window controller is part of a distributednetwork of controllers, wireless communication is used to transfer datato and from each of a plurality of electrochromic windows via thedistributed network of controllers, each having wireless communicationcomponents. For example, referring again to FIG. 11, master networkcontroller 1103, communicates wirelessly with each of intermediatenetwork controllers 1105 a and 1105 b, which in turn communicatewirelessly with end controllers 1110, each associated with anelectrochromic window. Master network controller 1103 may alsocommunicate wirelessly with the BMS. In one embodiment, at least onelevel of communication in the window controller is performed wirelessly.

In some embodiments, more than one mode of wireless communication isused in the window controller distributed network. For example, a masterwindow controller may communicate wirelessly to intermediate controllersvia WiFi or Zigbee, while the intermediate controllers communicate withend controllers via Bluetooth, Zigbee, EnOcean, or other protocol. Inanother example, window controllers have redundant wirelesscommunication systems for flexibility in end user choices for wirelesscommunication.

Wireless communication between, for example, master and/or intermediatewindow controllers and end window controllers offers the advantage ofobviating the installation of hard communication lines. This is alsotrue for wireless communication between window controllers and BMS. Inone aspect, wireless communication in these roles is useful for datatransfer to and from electrochromic windows for operating the window andproviding data to, for example, a BMS for optimizing the environment andenergy savings in a building. Window location data as well as feedbackfrom sensors are synergized for such optimization. For example, granularlevel (window-by-window) microclimate information is fed to a BMS inorder to optimize the building's various environments.

Although the foregoing disclosed embodiments have been described in somedetail to facilitate understanding, the described embodiments are to beconsidered illustrative and not limiting. It will be apparent to one ofordinary skill in the art that certain changes and modifications can bepracticed within the scope of the appended claims.

We claim:
 1. A method of limiting energy consumption in a facilityhaving at least one tintable window between an interior and exterior ofthe facility, wherein the level of tinting in the tintable window can becontrolled automatically, the method comprising: (a) receiving outputsignals from any two or more sensors selected from the group consistingof an exterior photosensor, an interior photosensor, an occupancysensor, an exterior temperature sensor, and a transmissivity sensorwhich detects light passing through the tintable window from theexterior; (b) determining a level of tint for said tintable window usinga relationship between the received output signals and the level oftint; and (c) providing instructions to change the tint of the tintablewindow to the level of tint determined in (b).
 2. The method of claim 1,further comprising applying voltage or current to the tintable window todrive the change in tint pursuant to the instructions provided in (c).3. The method of claim 1, wherein the relationship used in (b) reducesenergy consumption caused by a heating system, a cooling system, and/orlighting in the facility than otherwise would be caused, while providingconditions suitable for occupancy of the facility.
 4. The method ofclaim 1, further comprising receiving an energy or power consumptionsignal indicating energy or power consumption by a heating system, acooling system, and/or lighting in the facility, and using said energyor power consumption signal together with the received output signals in(a) to determine the level of tinting for said tintable window.
 5. Themethod of claim 1, wherein determining the level of tint in (b)comprises using scheduling information for the facility.
 6. The methodof claim 5, wherein the scheduling information comprises time of yearand/or time of day information for the facility.
 7. The method of claim6, wherein the scheduling information further comprises informationabout the geographical facing direction of the tintable window, a timeof day, and a latitude and a longitude of the facility.
 8. The method ofclaim 1, wherein the relationship employed in (b) is an expression inwhich the level of tint is the dependent variable and the output signalsare independent variables.
 9. The method of claim 1, wherein therelationship employed in (b) is a lookup table in which levels of tintare specified for various combinations of output signal values.
 10. Themethod of claim 1, wherein the relationship employed in (b) specifiesthe level of tint for said tintable window based, in part, on whetherthe window is transitioning from a darker tint to a lighter tint or froma lighter tint to a darker tint.
 11. The method of claim 1, wherein theoutput signals comprise the output signal from an exterior photosensor,and wherein the relationship employed in (b) requires (i) transitioningfrom a first lighter tint level to a second darker tint level when theoutput signal from the exterior photosensor passes a first threshold and(ii) transitioning from the second darker tint level to the firstlighter tint level when the output signal from the exterior photosensorpasses a second threshold, and wherein the first and second thresholdsare different.
 12. The method of claim 11, wherein the first thresholdis reached at a first value of irradiance and the second threshold isreached at a second value of irradiance, and the first value is greaterthan the second value.
 13. The method of claim 1, wherein the outputsignals comprise a signal from the exterior photosensor and a signalfrom the interior photosensor, and wherein the relationship employed in(b) is an expression or look up table in which the level of tint is thedependent variable and the signals from the exterior photosensor and theinterior photosensor are independent variables.
 14. The method of claim13, wherein the relationship employed in (b) uses scheduling informationcomprising time of year and/or time of day information for the facility.15. The method of claim 13, wherein the output signals further comprisea signal from the occupancy sensor, and wherein the relationshipemployed in (b) further employs the signal from the occupancy sensor.16. The method of claim 15, wherein the relationship employed in (b)further employs an energy or power consumption signal indicating energyor power consumption by a heating system, a cooling system, and/orlighting in the facility.
 17. The method of claim 16, wherein the levelof tint determined in (b) reduces energy consumption by a heatingsystem, a cooling system, and/or lighting in the facility whileproviding conditions suitable for occupancy of the facility.
 18. Acontroller for a tintable window for a facility having at least onetintable window between an interior and exterior of the facility, thecontroller comprising: (a) a processor or control circuit; (b) at leastone input for receiving output signals from one or more sensors; (c)instructions for causing the processor or control circuit to determine alevel of tint in said tintable window by using a relationship betweenthe received output signals and the level of tint, wherein therelationship employs output signals from any two or more sensorsselected from the group consisting of an exterior photosensor, aninterior photosensor, an occupancy sensor, an exterior temperaturesensor, and a transmissivity sensor which detects light passing throughthe tintable window from the exterior; and (d) at least one output forcontrolling, directly or indirectly, the level of tint in the tintablewindow.
 19. The controller of claim 18, further comprising a powersupply for applying voltage or current to the tintable window to drivethe change in tint to reach the level of tint determined by theinstructions.
 20. The controller of claim 18, further comprising logicfor receiving one or more of the output signals from a buildingmanagement system, a lighting control panel, or a security system forthe facility.
 21. The controller of claim 18, further comprising logicfor extracting one or more of the output signals from informationprovided by a building management system, a lighting control panel, or asecurity system for the facility.
 22. The controller of claim 18,further comprising a network interface for communicating with a networkcontaining a building management system for the facility, a lightingcontrol panel for the facility, and/or a security system for thefacility.
 23. The controller of claim 18, further comprising logic forreceiving an energy or power consumption signal indicating energy orpower consumption by a heating system, a cooling system, and/or lightingin the facility.
 24. The controller of claim 23, wherein theinstructions further comprise instructions for using said energy orpower consumption signal together with the received output signals indetermining the level of tinting for said tintable window.
 25. A systemfor controlling energy consumption in a facility that contains atintable window between an interior and exterior of the facility, thesystem comprising: (a) a building management system; (b) a lightingcontrol panel; (c) a network over which the building management systemand the lighting control panel communicate; and (d) a controller for thetintable window, the controller comprising (i) instructions fordetermining a level of tint in said tintable window by using arelationship between received output signals and the level of tint,wherein the relationship employs output signals from any two or moresensors selected from the group consisting of an exterior photosensor,an interior photosensor, an occupancy sensor, an exterior temperaturesensor, and a transmissivity sensor which detects light passing throughthe tintable window from the exterior, and (ii) at least one output forcontrolling, directly or indirectly, the level of tint in the tintablewindow.
 26. The system of claim 25, wherein the lighting control panelprovides occupancy information derived from the occupancy sensor, andwherein the relationship between received output signals and the levelof tint employs the occupancy information from the lighting controlpanel.
 27. A method of minimizing energy consumption in a facilityhaving a tintable window between an exterior and an interior of thefacility, wherein the tintable window has an adjustable level of tintcontrollable from a controller, the method comprising: (a) receiving asignal indicating energy or power consumption by a heating system, acooling system, and/or lighting within the facility; (b) determining alevel of tint for the tintable window using the signal indicating energyor power consumption of a device or system within the facility; and (c)providing instructions to set the level of tint in the tintable windowto the level determined in (b).
 28. The method of claim 27, furthercomprising monitoring the energy or power consumption of said heatingsystem, said cooling system, and/or said lighting of the facility toprovide the signal indicating energy or power consumption.
 29. Themethod of claim 27, wherein the device or system within the facilitycomprises a light, a group of lights, or a lighting system within thefacility.
 30. The method of claim 29, wherein the device or system withthe facility comprises at least one light located within about 20 feetof the tintable window.
 31. The method of claim 27, wherein the deviceor system within the facility comprises a heating or cooling device orsystem in the facility.
 32. The method of claim 31, wherein the deviceor system within the facility comprises at least one heating or coolingdevice located within about 50 feet of the tintable window.
 33. Acontroller for a tintable window for a facility having at least onetintable window between an interior and exterior of the facility, thecontroller comprising: (a) a processor or control circuit; (b) at leastone input for receiving output signals from one or more sensors; (c)instructions for causing the processor or control circuit to determine alevel of tint in said tintable window by using a relationship betweenthe received output signals and the level of tint, wherein therelationship employs output signals from an exterior photosensor, aninterior photosensor, an outside temperature sensor, and a tint command;and (d) at least one output for controlling, directly or indirectly, thelevel of tint in the tintable window.
 34. The controller of claim 33,further comprising a power supply for applying voltage or current to thetintable window to drive the change in tint to reach the level of tintdetermined by the instructions.
 35. The controller of claim 33, furthercomprising logic for receiving the output signals from the one or moresensors.
 36. The controller of claim 33, wherein the tint commandindicates a level of tint for the tintable window input by a person inthe facility.
 37. A method of limiting energy consumption in a facilityhaving at least one tintable window between an interior and exterior ofthe facility, wherein the level of tinting in the tintable window can becontrolled automatically, the method comprising: (a) receiving signalsindicating a level of exterior irradiance received at or proximate thetintable window; (b) determining a level of tint for said tintablewindow using a relationship between the received output signals and thelevel of tint, wherein the relationship requires (i) transitioning froma first lighter tint level to a second darker tint level when thereceived level of irradiance passes a first threshold and (ii)transitioning from the second darker tint level to the first lightertint level when the received level of irradiance passes a secondthreshold, and wherein the first and second thresholds are different;and (c) providing instructions to change the tint of the tintable windowto the level of tint determined in (b).
 38. The method of claim 37,wherein the first threshold is reached at a first value of irradianceand the second threshold is reached at a second value of irradiance, andthe first value is greater than the second value.
 39. The method ofclaim 37, further comprising: after a preset time elapses, repeatingoperations (a)-(c).
 40. The method of claim 37, further comprising:after a preset time elapses, repeating operation (a); and when there isa change in the received signals indicating the level of exteriorirradiance received at or proximate to the tintable window, repeatingoperations (b) and (c).